


crimson eyed beast

by DogMask



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap (Undertale), M/M, Other Additional Tags to Be Added, Tags Are Hard, Tags May Change, Underswap Alphys (Undertale), Underswap Papyrus (Undertale), Underswap Sans (Undertale), Underswap Toriel (Undertale), Underswap Undyne (Undertale), Undertale Monsters on the Surface
Language: English
Status: In-Progress
Published: 2021-02-24
Updated: 2021-02-24
Packaged: 2021-03-15 03:00:42
Rating: Mature
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 6
Words: 3,658
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29677380
Author URL: https://archiveofourown.org/users/DogMask/pseuds/DogMask
Summary: something's In the woods. something with bloodlust. something dangerous. something sinister. and it has its blood-red sights on blue.
Kudos: 2





	1. Chapter 1

**Author's Note:**

> NOTE: if you have a hard time imagining out what the creature looks like, imagine like- a midnight lycanroc, but bigger, mixed with one of those weird werewolves from the twilight series. cus why the hell not.

it was a typical day for papyrus. a very typical day. he went to Muffet's, got some more honey, saw his brother's mangled and bloodied form in the hospital. Ya'know, normal.

well, possibly not that last bit. sitting next to his brother, he sighed to himself. three out of five of the hours here he was yelling at every doctor in the place. they said a human found him outside the woods. barely alive. he still relived the moment he came in, the moment this officially became the worst reset ever:

_he rushed inside the white-painted room. his brother barely alive. his skull bruised, bloody and broken. he screamed. out of all the things he's seen, every reset he's been through, THIS was by far the goriest thing he had ever seen._

_checking his brother's soul, he made a chilling discovery: whatever did this to him. was far from human, and stronger than any boss monster he'd ever seen. "how...HOW DID THIS HAPPEN?!" he yelled at the first doctor he saw. but even as he talked, all he heard was static._

he was enraged- no **furious** if they went through all the trouble to go and find him, HOW THE HELL DID NO ONE SEE WHAT DID THIS TO HIM?! his eyesocket blazed orange. 'calm...down' he tried to remind himself. he could get angry after sans was healed.

looking at his brother, he softy rubbed his skull. he would fix this. even if he had to go hunt down this thing in the middle of the night. he promised. 


	2. Chapter 2

**Summary for the Chapter:**

> he didn't see him coming. he saw red. bloody fur. it hurt. so much.

BLUE'S POINT OF VIEW:

it hurts. everything hurts. the pain he felt...was more than physical. that animal- that....that...thing. it happened quickly.

too quickly. he was walking....or was he running? that thing hit him so hard...he could barely remember. 'focus' he tried to urge himself. remember. 

his name was sans. he had a brother named papyrus. he was training to be a police officer. why? so he could protect...yes, protect.

he stopped near the forest...because..because he heard a sound? no, because he saw blood.

yes. he saw blood. he followed it. wanted to help whatever bled...or was he curious....no, he wanted to help. he went into the woods....a-and..and...the thing...hurt...FOCUS! 

his name...h-his name was sans. he..had..he had a brother..named papyrus..he was training to......to be a..a police officer... to....protect...

His....his name...."BRO?!" what? what was that? he couldn't see, but felt something....something warm holding him..calling him....yes, yes his name was sans. his brother was with him now...he'll be ok...

just...

don't...

F0rgEt.


	3. Chapter 3

**Summary for the Chapter:**

> going on a creature hunt, goin on a creature hunt, gonna scare a teenager, gonna scare a teenager.

PAPYRUS'S POINT OF VIEW:

sans was still knocked out. it had been hours now, and I had to threaten a doctor within an inch of his life when he told me 'visiting' hours were over. too bad for visitors. I'd be leaving when my brother left. my brother....oh sans...his lower jaw was ripped off, the blood still dripping from where his lower canine teeth used to be, with claws running along his chest. both of his arms were broken and bruised, his poor eyesockets were outstretched.

claw marks surrounded the edges of them. "it's ok bro...you'll be ok" I lulled. I swear to Toriel.... when I find whatever the hell did this...

I wouldn't wanna be it. 

* * *

-THE NEXT DAY-

I was woken up by the nurse. she asked if sans had any medications he took. "unless you count milk, Nah." I dryly chuckled. sans always insisted on continuing to drink milk, in an attempt to get taller. can't complain though. milk IS good for the bones. heh. then I found out something...interesting. a cop came in, 'comforting' me by telling me that they found pawprints around his body. and they sent a human to go find it. which means; he will die a horrible death.

oh well. looks like I'm going animal-hunting. turning to sans I rubbed the top of his skull "I'll be back soon bro. don't get too bone-ly without me" I could practically hear him stifling a giggle. "love you, bro." I grin, teleporting outside the hospital, where I immediately got tackle-hugged. "RUS! IS HE OK?! IS HE HURT?! CAN I COME IN?!" my fluffy friend asked. "sh, shh calm down kid" I groaned as I pet his ear. Rex, a huge dog....wait. rex. huge dog. I'm, going on an animal-hunt. rex. huge dog. big claws. big teeth.

"Hey, kid? wanna help me find something?" just as I suspected, he immediately said yes. "c'mon kid. I suspect our friend is already gone." I smile, getting up. "ready?" "YUP!" with that, I teleported to that damned forest. the worst that could happen is me losing an arm. oh well. we walked for a while, nothing but mud, and trees. "s-so uh rus? I know that uh we're looking for something big, but uh....how big?" Rex slightly whined to me. "it's ok bud. I won't let any creepy crawlies hurt ya. tibia-honest, I don't think anyone WANTS to attack ya."

"RUUUS" he groaned before freezing. that can only mean one thing. "kid. stay very still. I don't wanna scare ya, but we are maybe in the territory of a murderer" right before a red-furred thing jumped him "SHIT" I summoned my blasters, but as I prepared to take fire, but that dickwad pulled rex in front of him, silently threatening to kill him. shit. this thing's smart. 

I took a good look at the furry thing. I could tell, this was an alpha male around here. it had crimson eyes, redder than blood. the same went for its fur. it has a mane full of white fluffy fur, with some of him being dark grey. it was big. bigger than Rex, by about 15 feet. fangs.

lots, and lots...of fangs. "ok...put the kid down feral dog thing. what do you want? for us to leave?" I slowly speak. he probably just sees us as trespassers. but he looked right at me and said "what I want....is that skeleton."....wait- this thing- this...creature..a-attacked....my brother. thinking fast I teleport and grab the kid. "RUN! NOW!" I pushed him through his portal he made. now, things could be fair. I shoot an array of blasters at him, but he dodged everyone.

bone attack. nothing. before I know it, he's in my face, glowing with a deep red aura. shit! "I teleport away, but it's too late, he grabbed onto my hoodie, and followed me out into the streets. FUCK! with no other choice, I use KARMA on him. he screamed. finally. "so you can feel pain" I chuckled. "I like blue on you more than red pal. it suits ya better." I used my blue attack. I landed five hits before he managed to free himself. 

he growled, but then stopped and grinned. never a good sign. "well, let me show you how I deal with guys like you." he charged at me, no chance to move away.

as I slowly blacked out, all I heard was: "Thanks for getting me a new playmate. c'mon. I have to train you now~" I felt him dragging me. 

sorry...bro...


	4. Chapter 4

**Notes for the Chapter:**

> imma make chapter this a time skip to a few months, cus nothing really happens to anyone before then.

BLUE'S P.O.V:

i...Did I open my eyes? I can see...I can see...wait...PAPY! I shot up, scanning for him. he wasn't anywhere in what looked like the room of a hospital. heat flashed painfully through my soul. oh gods it hurt! "pa..papy?" my voice...it sounded so different. why? I don't remember having this deep voice. oh I mean, I love it! but it's weird. I tried to get up, but machines were holding me. I flung them off with ease. 'good boy! you can get rid of that now~' a voice told me.

even more heated pains. "wha- huh? who're you?" I demanded. he..it sounded so angry. so....vengeful. 'aw, thank you blue. I am a he, and YOU, you lucky dog you, have not only been imprinted, but you have also been freed. call me Lycan~' "wh-wha...how do you know my name?! Who are you?! what's your name? why are you in my head? where's my brother? is that thing here?! what's going on?!" I asked rapidly. what on earth was this?!

'i know every freed friend's name. and I know you are worried about your brother. he is currently in the process of being saved!' he giggled. "so...you and I are...friends? and my brother is getting...saved? freed?" I ask skeptically "YES YOU SMART BOY! OOOH, I CANT WAIT TILL YOU COME TO MY PACK!' uh. weird. but as I began to question him the door opened, and a man in a white coat looked at me shockingly. "o-oh my god...it turned you..."I heard him softly cry.

'he's scared.' 'go in for the kill blue~' WHAT?! NO! I ignored him and kept trying to approach the man. but he yelled and begged for MERCY. more heat. Oh, gods how I hated this heat. it burned my bones, my soul, my very existence. and it only continued to hurt as I tried to help the poor guy. no such luck, as he kept yelling, and asking me how I could talk if I didn't have a bottom jaw. "I DONT HAVE A WHAT?!" 'he's right Lil blue. your lower jaw is completely gone. I think it suits you though. I'm helping you talk until we get you a replacement!' "GET OUT OF MY HEAD!" I yelled, almost forgetting about the man in front of me.

"p-please...I'll give you anything..please!" he pleaded. his....his fear..it..felt..nice? no! wrong!....but..he's so vulnerable...I could kill him now, and no one- NO! SNAP OUTTA IT SANS! 'oh don't sans. it's ok. just give in to your senses~ it'll feel soo much better.' yes. this man was prey. I was a predator? yes.

a predatory monster. I could see it now. one with claws, and fangs. a hunter, a predator; with blood-red eyes, and night vision. this heat in me..was just the old prey mind I had...trying to dissuade me into SPARING utterly fine food.

yes...eat...EaT...I closed the door and sunk my fangs into his arm. I felt cold. oh, how I loved that coolness on my bones. wait...no...NO WHAT ARE YOU DOING?! STOP! I pulled away from his now gushing bloody arm, and I saw fang marks on it. 'Why are you stopping sansy?~ I thought you WANTED to eat your prey. is that not the case anymore?' "NO! I DON'T! HE'S INNOCENT-" 'innocent prey. listen sans. in this world, there are the hunted, and the hunters.

I've given you a chance to be a prime, apex predatory hunter. just give in~ I assure you it'll be worthwhile~' another flash of painful heat hit m bones. n-no.....yes...prey...PrEy...I took a bite of him. soo good. 'that's right sansy...you keep eating~ growing κυνηγοί need their strngth~' "wh-wha...ok' one bite turned to two, two turned to three, soon enough, there was nothing left but his formerly white coat. I even ate the bones and drunk the spilled blood. organs included. 

what have I done...

'became a hunter. that's what'

* * *

Meanwhile; PAPYRUS'S P.O.V:

shit. this hurt. I and my new friend had been getting along swimmingly, him telling me he wanted to 'fix' me. I can't tell if this is from Stockholm syndrome or lack of food, but either way, I don't mind as much. he told me a friend of his was coming with my brother, who has already been saved. so he must fix me today. part of me hates his fluffy guts. the other part wants to please him; to be fixed for him. it's sick. and as hard as I try to hold onto the more sane part of me, I can hear it complaining less and less with each botched perfection attempt.

"howdy, bud! I finally figured out what'll break ya!" speak of the devil. no, he wasn't a devil. he was trying to help. "how so?" I asked. "turns out, skeletons have a...special spot, that helps...soothe them. and guess what dear friend, YOU are a skeleton!" he giddily cheered. I was....conflicted. "here we go! ready?" he asked. "ready as I'll ever be friend." here goes nothing..


	5. Chapter 5

**Summary for the Chapter:**

> blue and lycan. lycan and blue. poor paps...hopefully, lycan-blue can help him learn his place in their small pack.

PAPYRUS'S P.O.V:

as the furry demon chained me up to a new chair, I couldn't help but feel scared. what was it going to do to me? what did 'fixing' me have to do with my brother? why did he attack him in the first place?! "you have questions. I can tell. how's about I answer 'em while I prepare you for perfection?" the voice cut into me like the kid's old knife. he knew I was gonna break. I did too. "...fine. one: why did you attack my brother?" I ask, hoping to distract him. if I could just summon one sharp bone, I could try and cut through these damn binds. "I have done no such thing. I was trying to FIX him. as all broken things must be" he sighed as if he were talking to a completely different person. "why him?" I ask, I almost have that bone summoned. 

"his aura, it is beautiful. it is one of an apex predator. he has so much potential. and when my alpha told me to fix him, I was so honored. I suspect he is already learning of his primitive talents!" that scared me. "a-and..and what would he be learning?" I ask. one rope down, one to go. "why, to learn how to kill, destroy, fix, and obey the will of our alpha!" oh my god. sans? kill? no way "good luck with that bud, however..you just don't understand that my brother is NOT your personal project." I growled, silently standing over him. 

he simply turned to me, saying " you think you know everything about him yes? well if so, why did my alpha report to me he made his first kill, without a jaw?" he sneered. liar. I wasn't gonna fall for any more of his tricks. as I prepared to KR him, which I KNOW would kill the bastard, his damn grin only got bigger. "do it papyrus. kill me. show me you can be half the predator your brother is. or do you still need more training?" wait. no...no no no...I look back, and to my horror, I see a murky orange and cream tail. that bastard. every time he shocked, 'fixed' or beat me...he was making me into one of h i m.

"that's right paps. you aren't that bright. how did you not feel that until now? but I bet you won't KR me~" how DARE he. "try me." I prepared KR, but... I couldn't use it. no...it'd be stupid to dust him..when he could make me even better...NO! stop thinking like that! he imprisoned me! HE DEFIED THE LAWS OF NATURE BY MAKING A LITERAL SKELETON GROW A TAIL! HE DAMN NEAR KILLED SANS!.....but...no..fuck why is it so damn hot?! maybe...it wouldn't hurt..to..yea..maybe it wouldn't hurt to try and hear him out. 

NO! I pick him up growling. I didn't care. "you're gonna fix this. and then, your gonna fix my bro. or I could kill you now." I snarl, feeling fangs slowly poke out of my jaws. I truly don't care right now. "oh really? shame. looks like your brother will have to talk some sense into you." "HAH! like hell he would" I counter, before a door opens, a low growl is heard, and my small, jawless, and bloody brother pounces on me. holy hell. he was HUGE! "HIYA PAPS!" his voice...ugh. that voice did NOT belong to my brother.

I stumbled up trying not to look my 'brother' in the eyes. but in true papyrus fashion, I totally failed. his eyes... those once blue starred eyes turned blood-red, and..they were bright. almost as bright as- THAT DAMN DEVIL! I growled and came to my senses and grabbed him again. well, I tried. before I even got the chance to approach him, I felt sans's upper jaw tear into my bones, drawing a shit ton of marrow no. I couldn't fight my bro...but this was for his own good. "s-sans..you g-gotta...fight this...

I know it seems hard...but...this isn't you" I pleaded, not wanting to attack my little brother. the response I got was chilling. "papy, papy, papy." he started, taking his fangs out of my back. "I can tell you haven't had the chance to understand why this is needed. but please. unless we are alone, only address me- sorry, _us_ as lycan." right before he sunk his fangs into my neck. but this time, all I felt was warmth. _'lycan. he is our alpha'_ a voice told me. I must be...really tired...maybe...he wouldn't mind if i...took a small nap...right?

R I G H T ?


	6. Chapter 6

**Summary for the Chapter:**

> Lycan-blue has a little run-in with an old friend. and papyrus meets his new brain-roommate.

PAPYRUS'S P.O.V:  
As I slowly woke up, I heard a collection of voices. One sounded like my brother, but.... different. It was like...two voices into one. “come on omega! We only have two more hours until the initiation begins, and free prey walks in!” that voice..that was the thing that attacked him. “but of course, don’t rush to the point where you mess up my brother’s shifting.” now THAT voice I knew.   
That voice was my brother’s. I slowly open one of my eye sockets, and I wish I didn't. He was taller. He had not only a pair of white ears, but a tail to match, and from the bulge of his hands and shoes, his paws were on their way. It’s creepy to see him like this. Not just because he’s my brother, but because sans and I are skeletons. SKELETONS! how did they even manage to get ONE pair of ears on us?! 

‘calm yourself papyrus.’ holy fuck what was that? ‘language. I am just an unfortunate parasite to you.’ oh jeez I Gotta get sans and I out of here. “oh! Paps!” shit. Sans pulled me up with ease. This was what truly scared me. He lifted me, with one hand. “what’s that look for brother?” he grinned. looks like while I fell asleep my bro... regrew...his lower jaw. “heh, nothing bro. I just Uhm....nice jaw” ‘THAT was the best you could do??? THAT???’ oh shut up parasite, if you think it’s this easy, YOU do it.   
“uhhhh thanks, Paps! I need you to hold still for me, ok? This will only hurt a bit!” ‘if you Wanna survive to NOT be a bloodthirsty demon, run now or forever hold your peace.’ ok I got it. “Uhm no thanks bro.” too late. He bit me. And I felt.... warm? ‘that’s not warmth.’ oh...oh gods...Why is it getting hotter? ‘welp.’ “stay here Paps! I'll go get you a pre-hunt snack!” was all I heard right before passing out again. ‘you and I have to work on this passing out thing.’ W-...whatever.

* * *

NO ONE’S P.O.V:   
As Lycan-blue went out of the cabin their omega lived in, they softly thought about what to feed their brother. “raw human is always good, but Papy may not have the stomach for them yet.” blue thought. Lycan was grateful. It had taken weeks to get blue to accept his new state of mind, but oh it was so worth it.   
‘True, but the raw animal will be hard to find, so I say we just pick off a short one.’ he chimed. “clever idea!” and with that, Lycan-blue bounded out into the more popular part of the forest until they found an ideal man.

‘there. Look at that one. In perfect physical shape, but short.’ Lycan growled.   
They made a noise specific to the man’s soul, and just as they thought, he came into the deeper part of the woods and was in a perfect pouncing position. ‘let’s spare him for now. Paps might not appreciate if we steal his kill.’ blue told his alpha. ‘right.’   
They pounced, right before getting hit with an ax. Not just any ax, a magic ax. ‘oh, COME ON!’ blue growled lowly.

As Lycan-blue turned to see their attacker, a yellow lizard from the looks of it. She must’ve known blue because she looked at their tattered bandana and gasped, before extending her hand to them.   
“blue...is that you? Hey, c-come here.” she spoke softly. ‘she thinks we, are going to be intimidated by HER?’ Lycan asked confused. “...that’s not our name.” was all they muttered before taking the now unconscious man, not feeling like they WANTED to get more food. “b-blue! What do you mean ‘us?! Come back here!... IS THAT A TAIL?!” she gasped, before picking them up. 

A very dumb idea. Because as soon as she did, they took out her eye and damn near half of her face. the scream she let out was almost purr-inducing. they loved it when another monster feared them. as any smart creature should. hell, blue was scared of lycan due to his unpredictability, and lycan feared blue due to his extensive knowledge of souls, and magic. "WHAT THE HELL!" she screeched, before falling backward. "

wha- what ARE you? what did you to sans?" she asked as if she didn't already understand what was going on.   
grinning maliciously, they decided they should get a snack too. "we..." he started, opening his jaw "Are predators" he laughed, before ripping her arms off, and using said arms to rip open her ribcage.

**Notes for the Chapter:**

> ok, I admit it: I got that last part from venom. so sue me. (it was all I could think of)


End file.
